JP2006147389A - Measuring method of self discharge amount of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method of self discharge amount of a secondary battery with simplified measuring steps. <P>SOLUTION: The measuring method of self discharge amount of the secondary battery comprises a first means charging an object cell up to a voltage corresponding to an optional depth of discharge, a second means maintaining the set voltage by continuing the discharge for a prescribed period, and a third means measuring a charging current consumed for offsetting the lowering of voltage caused by capacity leakage generated during charging period. On the third means, the self discharge amount is calculated by defining the self discharge amount (Ah) as the product of a consumed current (A) and a charging period (h). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to a secondary battery used for an electronic component, a power supply device, a portable terminal device, and the like, and more particularly to a method for measuring a self-discharge amount of the secondary battery.

  A method for measuring the self-discharge amount of a conventional secondary battery will be described below. Conventionally, as a method of measuring the self-discharge amount, there is a method of measuring a decrease in terminal voltage after fully charging a battery and leaving it in a room temperature atmosphere for a certain period.

  A specific example will be described below. The conventional measuring method of the self-discharge amount is a measuring method using storage characteristics. For example, the battery is charged under rated conditions, and the charging condition is a current corresponding to a voltage of 4.2 V and 1 C. .5 hours at room temperature. In the rated charge state, a discharge capacity is measured by passing a current of 0.2 C, and this value becomes the initial discharge capacity. Next, it preserve | saves at 20 degreeC-30 days in a rated charge state, and measures the remaining capacity after a preservation | save next. Here, C is the discharge rate of the secondary battery.

  Here, the difference between the initial discharge capacity and the remaining capacity is the self-discharge amount.

  For example, as an example adopted in the delivery specification, there are provisions of capacity maintenance of 80% or more and self-discharge amount of 20% or less.

  FIG. 4 is an explanatory diagram of a conventional method for measuring the self-discharge amount of a secondary battery. In FIG. 4, the secondary battery is charged once and then left to stand to measure the voltage drop. Conventionally, the amount of voltage drop was obtained from the discharge curve of the secondary battery, and the amount of self-discharge was calculated by regarding this voltage drop as the amount of capacity reduction. Here, about 350 hours are spent measuring the self-discharge amount.

  For example, Patent Document 1 describes using a voltage drop of a terminal voltage as a method for measuring a self-discharge amount of a lithium ion secondary battery.

JP 2002-343446 A

  The conventional method for measuring the self-discharge amount of a secondary battery has the following problems. First, there is a problem that the measurement time is long. Secondly, there was a problem that the self-discharge amount was not directly measured for secondary batteries other than full charge (discharge depth 0%). For this reason, the amount of self-discharge is measured by converting the change in cell voltage after being left for a certain period into the change in capacity. Therefore, in the conventional measurement method, a period of about two weeks is necessary for the analysis of the cause of the defect from the customer, and in order to convert the voltage change into the capacity change, a secondary battery having the same characteristic is separately required. It was necessary to measure the discharge characteristic curve.

  Accordingly, an object of the present invention is to provide a method for measuring the self-discharge amount of a secondary battery with high measurement value reliability, which solves the above problems and simplifies the measurement procedure.

  The method for measuring the self-discharge amount of the secondary battery according to the present invention eliminates the conventional drawbacks. The secondary battery measures the charging current consumed to cancel the voltage drop due to capacity leakage during the charging period. This is a method for measuring the amount of self-discharge.

  That is, the present invention is a method for measuring a self-discharge amount of a secondary battery through constant voltage charging, wherein a first cell is set in a charging / discharging device and charged to a voltage corresponding to an arbitrary discharge depth; 2 by a second means for maintaining the set voltage by continuing charging for a certain period, and a third means for measuring the charging current consumed to offset the voltage drop due to capacity leakage during the charging period. A method for measuring a self-discharge amount of a secondary battery, wherein the third means calculates the self-discharge amount by current consumption (A) × charge period (h) = self-discharge amount (Ah). This is a method for measuring the amount of self-discharge.

  Further, in the present invention, in order to stabilize the voltage in the method for measuring the self-discharge amount of the secondary battery, the measurement is started from the time when one day has elapsed after the start of charging, and the current consumption (A) × charging period (H) = A measurement method of the self-discharge amount of the secondary battery in which the self-discharge amount is calculated by the self-discharge amount (Ah).

  As described above, according to the present invention, it is possible to provide a method for measuring the self-discharge amount of a secondary battery in a short period of time and with high reliability of measurement values, by simplifying the measurement procedure.

  A method for measuring the self-discharge amount of the secondary battery according to the embodiment of the present invention will be described below. The method for measuring the self-discharge amount of the secondary battery according to the present invention includes a first means for setting a target cell in a charge / discharge machine, and charging to a voltage corresponding to an arbitrary discharge depth, and continuing charging for a certain period. The method for measuring the self-discharge amount of the secondary battery by the second means for maintaining the set voltage and the third means for measuring the charging current consumed to cancel the voltage drop due to the capacity leakage during the charging period It is. A secondary battery characterized in that the third means calculates a self-discharge amount by defining a value obtained by multiplying a consumption current (A) and a charging period (h) as a self-discharge amount (Ah). The self-discharge amount is measured. Here, the range of the depth of discharge is a range of 0% (full charge) to 90% of the depth of discharge.

  Further, according to the present invention, in the method for measuring the self-discharge amount of the secondary battery, the third means starts measurement from the time when one day has elapsed after the start of charging in order to stabilize the voltage. This is a method for measuring the self-discharge amount of the secondary battery.

  FIG. 1 is an explanatory diagram of a method for measuring the self-discharge amount of the secondary battery of Example 1 of the present invention. Here, when the secondary battery used in FIG. 1 is about 2 years old after being manufactured and returned, in the case of a non-defective product, a battery with a voltage of 3.9 V in a 50% charged state has a voltage of 0 It was lowered to 5V.

  In FIG. 1, the horizontal axis represents the charging time, and the vertical axis represents the voltage, the dotted line represents the accumulated self-discharge amount, and the solid line represents the self-discharge. Indicates the amount. Here, the self-discharge amount is a discharge amount every 900 seconds, and the cumulative self-discharge amount is an integrated value of the self-discharge amount from the time point of one day. In the method for measuring the self-discharge amount of the secondary battery according to the present invention, in order to cancel the voltage drop due to the capacity leakage during the charging period, the measurement apparatus for measuring the charging current consumed with the voltage drop is provided. As shown in FIG. 1, the voltage is controlled to be 3.9V constant. This measurement shows that the amount of self-discharge of the secondary battery is quite high in a short period of time.

  FIG. 2 is an explanatory diagram of a method for measuring the self-discharge amount of the secondary battery of Example 2 of the present invention. Here, the secondary battery used in FIG. 2 has passed about 2.5 years after manufacture, and in the case of a non-defective product, a battery with a voltage of 3.9 V in a 50% charged state is up to a voltage of 2.5 V. The voltage was dropping.

  In FIG. 2, the horizontal axis represents the charging time, and the vertical axis represents the voltage, the dashed line represents the accumulated self-discharge amount, and the solid line represents the self-discharge. Indicates the amount. Here, the cumulative self-discharge amount is an integrated value of the self-discharge amount from the time point of one day. The method for measuring the self-discharge amount of the secondary battery according to the present invention has a third means for measuring the charging current consumed in association with the voltage drop in order to cancel the voltage drop due to capacity leakage during the charging period. This measurement shows that the self-discharge amount of the secondary battery is lower than that of Example 1.

  FIG. 3 is an explanatory diagram of a method for measuring the self-discharge amount of the secondary battery according to Example 3 of the present invention. Here, the secondary battery used in FIG. 3 is about 2 years old after manufacture. In the case of a non-defective product, the voltage of 3.9 V in the 50% charged state decreases to 1.9 V. It was.

  In FIG. 3, the horizontal axis represents the charging time, and the vertical axis represents the voltage, the dashed line represents the accumulated self-discharge amount, and the solid line represents the self-discharge. Indicates the amount. Here, the cumulative self-discharge amount is an integrated value of the self-discharge amount from the time point of one day. In the method for measuring the self-discharge amount of the secondary battery of the present invention, since there is a third means for measuring the charging current consumed to cancel the voltage drop due to capacity leakage during the charging period, It can be seen in a short time that the self-discharge amount is not so large.

  FIG. 5 is an explanatory diagram of a method for measuring the cumulative self-discharge amount of the secondary battery of Example 4 of the present invention. In FIG. 5, the horizontal axis represents the charging time, and the vertical axis represents the voltage, the dotted line represents the accumulated self-discharge amount, and the solid line represents the self time. Indicates the amount of discharge. In the method for measuring the self-discharge amount of the secondary battery of the present invention, since there is a third means for measuring the charging current consumed to cancel the voltage drop due to capacity leakage during the charging period, The self-discharge profile of good products can be grasped. Moreover, since a temporary profile can be grasped even in a short period, similarly, a defective product can be analyzed by comparing with a measurement of a defective product in a short period.

Explanatory drawing of the measuring method of the self-discharge amount of the secondary battery of Example 1 of this invention, and a cumulative self-discharge amount. Explanatory drawing of the measuring method of the self-discharge amount of the secondary battery of Example 2 of this invention, and a cumulative self-discharge amount. Explanatory drawing of the measuring method of the self-discharge amount of the secondary battery of Example 3 of this invention, and a cumulative self-discharge amount. Explanatory drawing of the measuring method of the self-discharge amount of the conventional secondary battery. Explanatory drawing of the measuring method of the self-discharge amount of the secondary battery of Example 4 of this invention, and a cumulative self-discharge amount.

Claims (3)

  A first means for setting the target cell in the charging / discharging device and charging to a voltage corresponding to an arbitrary discharge depth; a second means for maintaining the set voltage by continuing charging for a certain period; and during the charging period And a third means for measuring a charging current consumed to offset a voltage drop due to capacity leakage. A method for measuring a self-discharge amount of a secondary battery.   2. The method for measuring the self-discharge amount of the secondary battery, wherein the third means starts measurement after one day has elapsed after the start of charging in order to stabilize the voltage. The measuring method of the self-discharge amount of the secondary battery as described.
In the method for measuring the self-discharge amount of the secondary battery, the third means defines a value obtained by multiplying the consumption current (A) and the charging period (h) as the self-discharge amount (Ah) 3. The method for measuring the self-discharge amount of a secondary battery according to claim 1, wherein the self-discharge amount of the cell is calculated.

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